Integrated circuit dice, commonly called integrated circuit chips, are typically mounted inside packages having contacts extending therefrom for communication with the outside world. These contacts may be used to output signals from the chip, to input signals to the chip, or for supplying power or ground connections.
In conventional overmolded technology, a package is formed around the integrated circuit chip which may be mounted on a metal lead frame. The chip may be mechanically connected to the lead frame paddle or to the leads in the case of a lead-on-chip ("LOC") configuration. The chip assembly may also be electrically interconnected by fine wires from chip bond pads to a variety of lead frame fingers which connect to the exterior contacts on the package. The chip assembly is then positioned in a mold and the final package configuration is defined by plastic molding around the chip assembly. Since the lead frame assembly is relatively flexible, the position of the die with respect to the overmolded portion of the package is not necessarily fixed.
Conventionally, the overmolding or encapsulant, which may be a plastic or epoxy, protects and insulates not only the intervening die or chip but the lead frame and the wire bonding wires as well. With a chip assembly in a mold, the encapsulant is injected into the mold and air is exhausted from the opposite end of the mold.
The way the encapsulant enters the mold may cause the die to be displaced, either up or down depending on the lead frame, mold, and package design and on the encapsulation material and process. This may result in package bowing, stress location changes, increased delamination or cracking due to internal stress.
Thus, there is a need for techniques which help to maintain the die centered in overmolded packaging.